In <4.2 the following URL, passed as parameter, used to open the party with ID 220:
tryton://HOST:8000/DBNAME/model/party.party/220
In 4.2 however, an already open client instance just gets the focus but does no longer open the referenced record.
Tryton: 4.2 on Linux from http://debian.tryton.org/debian/dists/jessie-4.2/